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“Geared-Up” Pto-Driven Generator
Jeff Kohl, Northfield, Minn., wanted to have a pto-driven generator in case the electric power ever went out. However, he didn’t want to run his tractor’s engine at full throttle for an extended period of time in order to operate the pto shaft at 540 rpm’s. So he built a portable, 3-pt. mounted unit and fitted it with a 540 rpm pto shaft and a series of V-belts. The belts “gear up” a jackshaft that hooks up to the generator to operate it at the proper speed.
    “I use a 38 hp. diesel engine and a 540 rpm pto to operate it. The belt-driven unit lets me run the tractor engine at only about two thirds wide open. I’m operating the pto shaft at a slower speed than the generator requires, but this unit boosts the rpm’s,” says Kohl.
    “I finished building it last summer. I could have bought a commercial gas engine-powered generator, but it would have sat in my garage until I needed it. And I would have had to pull it out a couple times a year to keep it in operating condition. I can park my pto-driven generator in my garage for years until I need it.”
    The generator “cage” measures 30 in. wide, 36 in. long and 28 in. high and mounts on 4 caster wheels. Kohl bought a 13,000-watt, pto-driven North Star generator at a sale for $550. He used big bearings to mount the pto shaft in place and ran a long 1 1/4-in. dia. shaft to a big pulley on back. The pulley belt-drives 3 other pulleys that drive a jackshaft that hooks up to the generator.
     It needed 3,600 rpm’s in order to produce 120/240 Vac at 60 Hz. “Since a power unit needs 2 hp. per 1,000-watt generator, I needed a tractor with at least 26 hp.,” says Kohl.
    “All commercial pto-driven generators need the pto to run at 540 rpm’s, which means I would have to run my tractor’s engine at 2,600 rpm’s - almost full throttle - in order to produce a pto speed of 540 rpm’s. I didn’t want my tractor to run at full throttle for a long time, so I selected a tractor speed of 1,800 rpm’s as a goal for my generator. This would run my pto at 373.8 rpm’s.
    “To gear up the generator, I used some old pulleys I collected over the years. I had to do some math to figure out what I needed.
    “I spent a total of less than $1,000. I paid $100 for the pto shaft, $86 for the V-belts, and $60 for the caster wheels. It took me a long time to find all the parts that I needed. I got the angle iron, shafts and bearings free where I work.”
    Contact: FARM SHOW Followup, Jeff Kohl, 5259 130th Street East, Northfield, Minn. 55057 (ph 507 664-9439; mnbearus@hotmail.com).

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2018 - Volume #42, Issue #4